The price is about right for the type of battery it is however I'm suspicious of anything coming from China, Paypal offer some protection against counterfeit goods although that's assuming it's clearly a fake.

I'm a bit wary about the feedback as no-one specifically says whether the battery is genuine or not, it's all a bit vague. I've seen similar auctions where no-one has explicitly said it's a fake but then I've received a fake.